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第1行： − + − {{Other uses}}+ − 其他用途 − {{short description|Process where information about current status is used to influence future status}}+ − 简述|利用当前状态信息影响未来状态的过程 − − {{Use dmy dates|date=September 2020}} − 使用dmy日期|日期=2020年9月 − − {{Complex systems}}[[File:General Feedback Loop.svg|thumb|A feedback loop where all outputs of a process are available as causal inputs to that process]] − − − A feedback loop where all outputs of a process are available as causal inputs to that process − − 一个反馈回路过程的所有输出都可作为该过程的因果输入。 − − − − '''Feedback''' occurs when outputs of a system are routed back as inputs as part of a [[Signal chain (signal processing chain)|chain]] of [[Causality|cause-and-effect]] that forms a circuit or loop.<ref name=Ford>{{cite book |title=Modeling the Environment |author=Andrew Ford |chapter=Chapter 9: Information feedback and causal loop diagrams |pages=99 ''ff'' |publisher=Island Press |year=2010 |isbn=9781610914253 |chapter-url=https://books.google.com/books?id=38PJahZTzC0C&pg=PA99lpg |quote=This chapter describes [[causal loop diagram]]s to portray the information feedback at work in a system. The word ''causal'' refers to cause-and-effect relationships. The word''loop'' refers to a closed chain of cause and effect that creates the feedback.}}</ref> The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems: − − Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to feed back into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems: − − 当一个系统的输出作为输入被送回，并作为形成回路或循环的因果链的一部分时，就会产生<font color="#ff8000"> 反馈 feedback</font>。<ref name=Ford>{{cite book |title=Modeling the Environment |author=Andrew Ford |chapter=Chapter 9: Information feedback and causal loop diagrams |pages=99 ''ff'' |publisher=Island Press |year=2010 |isbn=9781610914253 |chapter-url=https://books.google.com/books?id=38PJahZTzC0C&pg=PA99lpg |quote=This chapter describes [[causal loop diagram]]s to portray the information feedback at work in a system. The word ''causal'' refers to cause-and-effect relationships. The word''loop'' refers to a closed chain of cause and effect that creates the feedback.}}</ref>这个系统可以说是反馈到了自身。在因果关系应用于反馈系统时，必须谨慎处理其概念。 − − − {{quote − |text=Simple causal reasoning about a feedback system is difficult because the first system influences the second and second system influences the first, leading to a circular argument. This makes reasoning based upon cause and effect tricky, and it is necessary to analyze the system as a whole. − |author=Karl Johan Åström and Richard M.Murray − |title=''Feedback Systems: An Introduction for Scientists and Engineers''<ref>{{cite book |title=Feedback Systems: An Introduction for Scientists and Engineers |author1=Karl Johan Åström |author2=Richard M. Murray |chapter=§1.1: What is feedback? |chapter-url=https://books.google.com/books?id=cdG9fNqTDS8C&q=%22This+makes+reasoning+based+on+cause+and+effect+tricky%22&pg=PA1 |isbn= 9781400828739 |year=2008 |page=1 |publisher=Princeton University Press}} Online version found [http://authors.library.caltech.edu/25062/1/Feedback08.pdf here].</ref>}} − − {{quote − |text=Simple causal reasoning about a feedback system is difficult because the first system influences the second and second system influences the first, leading to a circular argument. This makes reasoning based upon cause and effect tricky, and it is necessary to analyze the system as a whole. − |author=Karl Johan Åström and Richard M.Murray − |title=Feedback Systems: An Introduction for Scientists and Engineers}} − − − {{引用 − 对于一个反馈系统，很难进行简单的因果推理，因为第一个系统影响第二个系统，第二个系统影响第一个系统，产生了一个循环论证。这就使得基于因果关系的推理变得很困难，因此有必要将系统作为一个整体进行分析。 − |作者:卡尔·约翰·阿斯特洛姆 · 马丁 Karl Johan Åström和查德 · M · 默里 Richard M.Murray − | title = 反馈系统: 科学家和工程师介绍<ref>{{cite book |title=Feedback Systems: An Introduction for Scientists and Engineers |author1=Karl Johan Åström |author2=Richard M. Murray |chapter=§1.1: What is feedback? |chapter-url=https://books.google.com/books?id=cdG9fNqTDS8C&q=%22This+makes+reasoning+based+on+cause+and+effect+tricky%22&pg=PA1 |isbn= 9781400828739 |year=2008 |page=1 |publisher=Princeton University Press}} Online version found [http://authors.library.caltech.edu/25062/1/Feedback08.pdf here].</ref>} − − − − − ==History== − 历史 − − Self-regulating mechanisms have existed since antiquity, and the idea of feedback had started to enter [[Economics|economic theory]] in Britain by the 18th century, but it was not at that time recognized as a universal abstraction and so did not have a name.<ref name=mayr>{{Cite book |author= Otto Mayr|title=Authority, liberty, & automatic machinery in early modern Europe |year=1989 |isbn=978-0-8018-3939-9 | publisher=Johns Hopkins University Press |author-link=Otto Mayr }}</ref> − − Self-regulating mechanisms have existed since antiquity, and the idea of feedback had started to enter economic theory in Britain by the 18th century, but it was not at that time recognized as a universal abstraction and so did not have a name. + − − − The first ever known artificial feedback device was a [[Ballcock|float valve]], for maintaining water at a constant level, invented in 270 BC in [[Alexandria]], [[Ancient Egypt|Egypt]].<ref name=":0">{{Cite book|title=Designing Kinetics for Architectural Facades|last=Moloney|first=Jules|publisher=Routledge|year=2011|isbn=978-0415610346}}</ref> This device illustrated the principle of feedback: a low water level opens the valve, the rising water then provides feedback into the system, closing the valve when the required level is reached. This then reoccurs in a circular fashion as the water level fluctuates.<ref name=":0" /> − − The first ever known artificial feedback device was a float valve, for maintaining water at a constant level, invented in 270 BC in Alexandria, Egypt. This device illustrated the principle of feedback: a low water level opens the valve, the rising water then provides feedback into the system, closing the valve when the required level is reached. This then reoccurs in a circular fashion as the water level fluctuates. − + − [[Centrifugal governor]]s were used to regulate the distance and pressure between [[millstone]]s in [[windmill]]s since the 17th century. In 1788, [[James Watt]] designed his first centrifugal governor following a suggestion from his business partner [[Matthew Boulton]], for use in the [[steam engine]]s of their production. Early steam engines employed a purely [[reciprocating motion]], and were used for pumping water – an application that could tolerate variations in the working speed, but the use of steam engines for other applications called for more precise control of the speed. − − Centrifugal governors were used to regulate the distance and pressure between millstones in windmills since the 17th century. In 1788, James Watt designed his first centrifugal governor following a suggestion from his business partner Matthew Boulton, for use in the steam engines of their production. Early steam engines employed a purely reciprocating motion, and were used for pumping water – an application that could tolerate variations in the working speed, but the use of steam engines for other applications called for more precise control of the speed. − − 自17世纪以来，[[离心调速器]]被用于调节[[风车]]中[[磨石]]之间的距离和压力。1788年，詹姆斯·瓦特 James Watt根据他的商业伙伴马修·布尔顿 Matthew Boulton的建议，设计了他的第一个离心调速器，应用于他们生产的[[蒸汽机]]。早期的蒸汽机采用纯粹的[[往复运动]]，用于抽水——这种应用不受工作速度变化的影响，但蒸汽机在其他应用中的使用需要更精确的速度控制。 − − − In [[1868]], [[James Clerk Maxwell]] wrote a famous paper, "On governors", that is widely considered a classic in feedback control theory.<ref>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|journal=Proceedings of the Royal Society of London|volume= 16|year= 1868 |pages= 270–283 | doi = 10.1098/rspl.1867.0055 | jstor=112510|doi-access=free}}</ref> This was a landmark paper on [[control theory]] and the mathematics of feedback. − − In 1868, James Clerk Maxwell wrote a famous paper, "On governors", that is widely considered a classic in feedback control theory.This was a landmark paper on [[control theory]] and the mathematics of feedback. − − − The verb phrase ''to feed back'', in the sense of returning to an earlier position in a mechanical process, was in use in the US by the 1860s,<ref>''"Heretofore ... it has been necessary to reverse the motion of the rollers, thus causing the material to travel or feed back, ..."'' HH Cole, "Improvement in Fluting-Machines", [http://www.google.co.nz/patents/US55469 US Patent 55,469 (1866)] accessed 23 March 2012.</ref><ref>''"When the journal or spindle is cut ... and the carriage is about to feed back by a change of the sectional nut or burr upon the screw-shafts, the operator seizes the handle..."'' JM Jay, "Improvement in Machines for Making the Spindles of Wagon-Axles", [http://www.google.co.nz/patents/US47769 US Patent 47,769 (1865)] accessed 23 March 2012. Maintaining a desired system performance despite disturbance using negative feedback to reduce system error</ref> and in 1909, Nobel laureate [[Karl Ferdinand Braun]] used the term "feed-back" as a noun to refer to (undesired) [[Coupling (electronics)|coupling]] between components of an [[electronic circuit]].<ref>''"...as far as possible the circuit has no feed-back into the system being investigated."'' − An example of a negative feedback loop with goals − [http://www.cdvandtext2.org/Braun-Nobel-lecture%201909.pdf] − A positive feedback loop example − Karl Ferdinand Braun, [https://www.nobelprize.org/nobel_prizes/physics/laureates/1909/braun-lecture.html "Electrical oscillations and wireless telegraphy"], Nobel Lecture, 11 December 1909. Retrieved 19 March 2012.</ref> − − The verb phrase to feed back, in the sense of returning to an earlier position in a mechanical process, was in use in the US by the 1860s, and in 1909, Nobel laureate Karl Ferdinand Braun used the term "feed-back" as a noun to refer to (undesired) coupling between components of an electronic circuit. 第92行：
第22行： + − By the end of 1912, researchers using early electronic amplifiers ([[audion tube|audions]]) had discovered that deliberately coupling part of the output signal back to the input circuit would boost the amplification (through [[Regenerative circuit|regeneration]]), but would also cause the audion to howl or sing.<ref name="bennett">{{Cite book|url=http://worldcat.org/isbn/0-906-04807-9|title=A history of control engineering, 1800–1930|author=Stuart Bennett|publisher=Peregrinus for the Institution of Electrical Engineers|year=1979|isbn=978-0-906048-07-8|location=Stevenage; New York}} </ref> This action of feeding back of the signal from output to input gave rise to the use of the term "feedback" as a distinct word by 1920.<ref name=bennett/>+ − − By the end of 1912, researchers using early electronic amplifiers (audions) had discovered that deliberately coupling part of the output signal back to the input circuit would boost the amplification (through regeneration), but would also cause the audion to howl or sing. This action of feeding back of the signal from output to input gave rise to the use of the term "feedback" as a distinct word by 1920. − − 到1912年底，研究人员利用早期电子放大器(三极管)发现，故意将部分输出信号耦合回输入电路，会提高放大率(形成再生回路)，但也会使三极管发生啸叫。<ref name="bennett">{{Cite book|url=http://worldcat.org/isbn/0-906-04807-9|title=A history of control engineering, 1800–1930|author=Stuart Bennett|publisher=Peregrinus for the Institution of Electrical Engineers|year=1979|isbn=978-0-906048-07-8|location=Stevenage; New York}} </ref>这种将信号从输出反馈到输入的行为使得 "反馈 "一词在1920年被作为一个独立的词汇使用。<ref name=bennett/> − − − Over the years there has been some dispute as to the best definition of feedback. According to [[William Ross Ashby|Ashby]] (1956), mathematicians and theorists interested in the principles of feedback mechanisms prefer the definition of "circularity of action", which keeps the theory simple and consistent. For those with more practical aims, feedback should be a deliberate effect via some more tangible connection. − − Over the years there has been some dispute as to the best definition of feedback. According to Ashby (1956), mathematicians and theorists interested in the principles of feedback mechanisms prefer the definition of "circularity of action", which keeps the theory simple and consistent. For those with more practical aims, feedback should be a deliberate effect via some more tangible connection. − − − − − {{Quote|[Practical experimenters] object to the mathematician's definition, pointing out that this would force them to say that feedback was present in the ordinary pendulum ... between its position and its momentum—a "feedback" that, from the practical point of view, is somewhat mystical. To this the mathematician retorts that if feedback is to be considered present only when there is an actual wire or nerve to represent it, then the theory becomes chaotic and riddled with irrelevancies.<ref name=Ashby>。{{cite book |author=W. Ross Ashby |title=An introduction to cybernetics |publisher=Chapman & Hall |year=1957 |url=http://pcp.vub.ac.be/books/IntroCyb.pdf}}</ref>{{rp|page=54}}}} − − {{引言|[实际实验者]反对数学家的定义，指出这将迫使他们说普通的摆.中存在反馈.....在其位置和动量之间——这种 "反馈"，从实际的角度看，有些神秘。对此，数学家反驳说，如果只有用实际的导线或神经来表示反馈时，才认为反馈是存在的，那么这个理论就会变得混乱，充满了无关紧要的东西<ref name=Ashby>。{{cite book |author=W. Ross Ashby |title=An introduction to cybernetics |publisher=Chapman & Hall |year=1957 |url=http://pcp.vub.ac.be/books/IntroCyb.pdf}}</ref>{{rp|page=54}}}} − − − Focusing on uses in management theory, Ramaprasad (1983) defines feedback generally as "...information about the gap between the actual level and the reference level of a system parameter" that is used to "alter the gap in some way". He emphasizes that the information by itself is not feedback unless translated into action.<ref name="Ramaprasad">{{Cite journal | doi=10.1002/bs.3830280103|title = On the definition of feedback| journal=Behavioral Science| volume=28| pages=4–13|year = 1983|last1 = Ramaprasad|first1 = Arkalgud}}</ref> − − Focusing on uses in management theory, Ramaprasad (1983) defines feedback generally as "...information about the gap between the actual level and the reference level of a system parameter" that is used to "alter the gap in some way". He emphasizes that the information by itself is not feedback unless translated into action. − − 拉马普拉萨德 Ramaprasad (1983)侧重于反馈在管理理论中的用途，他通常将反馈定义为"……关于系统参数的实际水平与参考水平之间差距的信息"，用于 "以某种方式改变差距"。他强调，信息本身不是反馈，转化为行动才是。<ref name="Ramaprasad">{{Cite journal | doi=10.1002/bs.3830280103|title = On the definition of feedback| journal=Behavioral Science| volume=28| pages=4-13|year = 1983|last1 = Ramaprasad|first1 = Arkalgud}}</ref>。 − − − − − − ==Types== − 类型 − − ===Positive and negative feedback=== − 正反馈和负反馈 − − {{Main|Negative feedback|Positive feedback}} − 主要|负反馈|正反馈 − − [[File:Set-point control.png|thumb|350px|Maintaining a desired system performance despite disturbance using negative feedback to reduce system error]] − − [[File:Set-point control.png|thumb|350px|利用负反馈减少系统误差，在受到干扰的情况下仍能保持理想的系统性能]] − − − [[File:Outcome Feedback Negative Feedback Loop.png|thumb|An example of a negative feedback loop with goals]] − − [[[File:Outcome Feedback Negative Feedback Loop.png|thumb|拇指|目标负反馈循环的示例]] − − − [[File:Process Feedback Loop.png|thumb|A positive feedback loop example]] − [[File：Process Feedback Loop.png | thumb |正反馈循环示例]] − − − Positive feedback: If the signal fed back from output is in phase with the input signal, the feedback is called positive feedback. − − <font color="#ff8000"> 正反馈 Positive feedback</font>: 如果输出的反馈信号与输入信号同相，则称为正反馈。 + − Negative feedback: If the signal fed back is of opposite polarity or out of phase by 180° with respect to input signal, the feedback is called as negative feedback.+ − <font color="#ff8000"> 负反馈 Negative feedback</font>: 如果反馈信号与输入信号的极性相反或相位相差180°，则称为负反馈。+ + + + + − As an example of negative feedback, the diagram might represent a cruise control system in a car, for example, that matches a target speed such as the speed limit. The controlled system is the car; its input includes the combined torque from the engine and from the changing slope of the road (the disturbance). The car's speed (status) is measured by a speedometer. The error signal is the departure of the speed as measured by the speedometer from the target speed (set point). This measured error is interpreted by the controller to adjust the accelerator, commanding the fuel flow to the engine (the effector). The resulting change in engine torque, the feedback, combines with the torque exerted by the changing road grade to reduce the error in speed, minimizing the road disturbance.+ − 该图表示的汽车中的巡航控制系统可以作为负反馈的一个例子，它使车速与目标速度(如车速限制)匹配。受控系统是汽车，其输入包括来自发动机和来自路面变化的坡度(干扰)的组合扭矩。汽车的速度(状态)由速度表测量。误差信号是速度计测量的速度与目标速度（设定点）的偏差。这个测量的误差由控制器来解译并以此来调整加速器，控制燃料流到发动机(效应器)。由此产生的发动机扭矩的变化，即反馈，与路面变化的坡度所施加的扭矩相结合，以减少速度误差，减少道路干扰。+
无编辑摘要
本词条由11初步翻译，已由WildBoar完成审校。
本词条由11初步翻译，已由WildBoar完成审校。
https://wiki.swarma.org/index.php?title=%E5%B9%B3%E8%A1%A1%E7%90%86%E8%AE%BA#:~:text=%E6%9C%AC%E8%AF%8D%E6%9D%A1%E7%94%B1,11%E5%88%9D%E6%AD%A5%E7%BF%BB%E8%AF%91
当一个系统的输出作为输入被送回，并作为形成回路或循环的因果链的一部分时，就会产生'''反馈 feedback'''。<ref name=Ford>{{cite book |title=Modeling the Environment |author=Andrew Ford |chapter=Chapter 9: Information feedback and causal loop diagrams |pages=99 ''ff'' |publisher=Island Press |year=2010 |isbn=9781610914253 |chapter-url=https://books.google.com/books?id=38PJahZTzC0C&pg=PA99lpg |quote=This chapter describes [[causal loop diagram]]s to portray the information feedback at work in a system. The word ''causal'' refers to cause-and-effect relationships. The word''loop'' refers to a closed chain of cause and effect that creates the feedback.}}</ref>这个系统可以说是反馈到了自身。在因果关系应用于反馈系统时，必须谨慎处理其概念。
对于一个反馈系统，很难进行简单的因果推理，因为第一个系统影响第二个系统，第二个系统影响第一个系统，产生了一个循环论证。这就使得基于因果关系的推理变得很困难，因此有必要将系统作为一个整体进行分析。——卡尔·约翰·阿斯特洛姆·马丁 Karl Johan Åström和查德·M·默里 Richard M.Murray
[[文件:复杂系统.jpg|缩略图|右|复杂系统]]
==历史==
自我调节机制自古以来就存在，直到18世纪，反馈的概念开始进入英国的经济理论，但当时它还不是一个普遍的抽象概念，因此没有名称。<ref name=mayr>{{Cite book |author= Otto Mayr|title=Authority, liberty, & automatic machinery in early modern Europe |year=1989 |isbn=978-0-8018-3939-9 | publisher=Johns Hopkins University Press |author-link=Otto Mayr }}</ref>
自我调节机制自古以来就存在，直到18世纪，反馈的概念开始进入英国的经济理论，但当时它还不是一个普遍的抽象概念，因此没有名称。<ref name=mayr>{{Cite book |author= Otto Mayr|title=Authority, liberty, & automatic machinery in early modern Europe |year=1989 |isbn=978-0-8018-3939-9 | publisher=Johns Hopkins University Press |author-link=Otto Mayr }}</ref>
第一个已知的人工反馈装置是公元前270年在埃及亚历山大发明的用于保持水位恒定的浮阀。<ref name=":0">{{Cite book|title=Designing Kinetics for Architectural Facades|last=Moloney|first=Jules|publisher=Routledge|year=2011|isbn=978-0415610346}}</ref>这个装置说明了反馈的原理：低水位打开阀门，上升的水位向系统提供反馈，达到所需水位时关闭阀门。然后，这种情况会随着水位的波动循环地重复发生。<ref name=":0" />
第一个已知的人工反馈装置是公元前270年在埃及亚历山大发明的用于保持水位恒定的浮阀。<ref name=":0">{{Cite book|title=Designing Kinetics for Architectural Facades|last=Moloney|first=Jules|publisher=Routledge|year=2011|isbn=978-0415610346}}</ref>这个装置说明了反馈的原理：低水位打开阀门，上升的水位向系统提供反馈，达到所需水位时关闭阀门。然后，这种情况会随着水位的波动循环地重复发生。<ref name=":0" />
自17世纪以来，离心调速器被用于调节风车中磨石之间的距离和压力。1788年，詹姆斯·瓦特 James Watt根据他的商业伙伴马修·布尔顿 Matthew Boulton的建议，设计了他的第一个离心调速器，应用于他们生产的蒸汽机。早期的蒸汽机采用纯粹的往复运动，用于抽水——这种应用不受工作速度变化的影响，但蒸汽机在其他应用中的使用需要更精确的速度控制。
在1868年，詹姆斯·克莱克·麦克斯韦 James Clerk Maxwell写了一篇著名的论文《论调速器》，这个论文被广泛认为是反馈控制理论的经典之作。<ref>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|journal=Proceedings of the Royal Society of London|volume= 16|year= 1868 |pages= 270–283 | doi = 10.1098/rspl.1867.0055 | jstor=112510|doi-access=free}}</ref>这是一篇关于控制理论和反馈数学的里程碑式的论文。
在1868年，詹姆斯·克莱克·麦克斯韦 James Clerk Maxwell写了一篇著名的论文《论调速器》，这个论文被广泛认为是反馈控制理论的经典之作。<ref>{{cite journal|last=Maxwell|first=James Clerk|title=On Governors|journal=Proceedings of the Royal Society of London|volume= 16|year= 1868 |pages= 270–283 | doi = 10.1098/rspl.1867.0055 | jstor=112510|doi-access=free}}</ref>这是一篇关于控制理论和反馈数学的里程碑式的论文。
19世纪60年代，美国开始使用关于反馈的动词短语，意思是在机械过程中回到原来的位置。<ref>''"Heretofore ... it has been necessary to reverse the motion of the rollers, thus causing the material to travel or feed back, ..."'' HH Cole, "Improvement in Fluting-Machines", [http://www.google.co.nz/patents/US55469 US Patent 55,469 (1866)] accessed 23 March 2012.</ref><ref>''"When the journal or spindle is cut ... and the carriage is about to feed back by a change of the sectional nut or burr upon the screw-shafts, the operator seizes the handle..."'' JM Jay, "Improvement in Machines for Making the Spindles of Wagon-Axles", [http://www.google.co.nz/patents/US47769 US Patent 47,769 (1865)] accessed 23 March 2012. Maintaining a desired system performance despite disturbance using negative feedback to reduce system error</ref> 1909年，诺贝尔奖获得者卡尔·费迪南德·布劳恩 Karl Ferdinand Braun用名词“反馈”来指电子电路元件之间的(不希望有的)耦合。<ref>''"...as far as possible the circuit has no feed-back into the system being investigated."''
19世纪60年代，美国开始使用关于反馈的动词短语，意思是在机械过程中回到原来的位置。<ref>''"Heretofore ... it has been necessary to reverse the motion of the rollers, thus causing the material to travel or feed back, ..."'' HH Cole, "Improvement in Fluting-Machines", [http://www.google.co.nz/patents/US55469 US Patent 55,469 (1866)] accessed 23 March 2012.</ref><ref>''"When the journal or spindle is cut ... and the carriage is about to feed back by a change of the sectional nut or burr upon the screw-shafts, the operator seizes the handle..."'' JM Jay, "Improvement in Machines for Making the Spindles of Wagon-Axles", [http://www.google.co.nz/patents/US47769 US Patent 47,769 (1865)] accessed 23 March 2012. Maintaining a desired system performance despite disturbance using negative feedback to reduce system error</ref> 1909年，诺贝尔奖获得者卡尔·费迪南德·布劳恩 Karl Ferdinand Braun用名词“反馈”来指电子电路元件之间的(不希望有的)耦合。<ref>''"...as far as possible the circuit has no feed-back into the system being investigated."''
Karl Ferdinand Braun, [https://www.nobelprize.org/nobel_prizes/physics/laureates/1909/braun-lecture.html "Electrical oscillations and wireless telegraphy"], Nobel Lecture, 11 December 1909. Retrieved 19 March 2012.</ref>
Karl Ferdinand Braun, [https://www.nobelprize.org/nobel_prizes/physics/laureates/1909/braun-lecture.html "Electrical oscillations and wireless telegraphy"], Nobel Lecture, 11 December 1909. Retrieved 19 March 2012.</ref>
到1912年底，研究人员利用早期电子放大器（三极管）发现，故意将部分输出信号耦合回输入电路，会提高放大率（形成再生回路），但也会使三极管发生啸叫。<ref name="bennett">{{Cite book|url=http://worldcat.org/isbn/0-906-04807-9|title=A history of control engineering, 1800–1930|author=Stuart Bennett|publisher=Peregrinus for the Institution of Electrical Engineers|year=1979|isbn=978-0-906048-07-8|location=Stevenage; New York}} </ref>这种将信号从输出反馈到输入的行为使得“反馈”一词在1920年被作为一个独立的词汇使用。<ref name=bennett/>
多年来，关于反馈的最佳定义一直存在一些争议。根据阿什比 Ashby（1956）的说法。对反馈机制原理感兴趣的数学家和理论家倾向于用“作用的循环性”来定义反馈，这使理论保持简洁和一致。对于那些有更实际目的的人来说，反馈应该是具体过程产生的特定的影响。
多年来，关于反馈的最佳定义一直存在一些争议。根据阿什比 Ashby(1956)的说法。对反馈机制原理感兴趣的数学家和理论家倾向于用 "作用的循环性 "来定义反馈，这使理论保持简洁和一致。对于那些有更实际目的的人来说，反馈应该是具体过程产生的特定的影响。
实际实验者反对数学家的定义，指出这将迫使他们说，反馈存在于普通的钟摆中。在其位置和动量之间——一种从实际角度看有点神秘的“反馈”。对此，数学家反驳说，如果只有用实际的导线或神经来表示反馈时才认为反馈是存在的，那么这个理论就会变得混乱，充满了无关紧要的东西。<ref name=Ashby>。{{cite book |author=W. Ross Ashby |title=An introduction to cybernetics |publisher=Chapman & Hall |year=1957 |url=http://pcp.vub.ac.be/books/IntroCyb.pdf}}</ref>{{rp|page=54}}}}
拉马普拉萨德 Ramaprasad（1983）侧重于反馈在管理理论中的用途，他通常将反馈定义为“……关于系统参数的实际水平与参考水平之间差距的信息”，用于“以某种方式改变差距”。他强调，信息本身不是反馈，转化为行动才是。<ref name="Ramaprasad">{{Cite journal | doi=10.1002/bs.3830280103|title = On the definition of feedback| journal=Behavioral Science| volume=28| pages=4-13|year = 1983|last1 = Ramaprasad|first1 = Arkalgud}}</ref>。
==类型==
===正反馈和负反馈===
[[文件:结果反馈负反馈循环.jpg|缩略图|右|一个有目标的负反馈循环的例子。]]
[[文件:过程反馈回路.jpg|缩略图|右|一个正反馈循环的例子。]]
'''正反馈 Positive feedback'''：如果输出的反馈信号与输入信号同相，则称为正反馈。
'''负反馈 Negative feedback'''：如果反馈信号与输入信号的极性相反或相位相差180°，则称为负反馈。
该图表示的汽车中的巡航控制系统可以作为负反馈的一个例子，它使车速与目标速度（如车速限制）匹配。受控系统是汽车，其输入包括来自发动机和来自路面变化的坡度（干扰）的组合扭矩。汽车的速度（状态）由速度表测量。误差信号是速度计测量的速度与目标速度（设定点）的偏差。这个测量的误差由控制器来解译并以此来调整加速器，控制燃料流到发动机（效应器）。由此产生的发动机扭矩的变化，即反馈，与路面变化的坡度所施加的扭矩相结合，以减少速度误差，减少道路干扰。